1. Field of the Invention
The present invention is generally directed toward an apparatus for the internal fixation of fractures of tubular bones by compression.
2. Brief Description of the Background
Currently, fractured tubular bones are transfixed surgically by either metal plates and screws or intramedullary metal rods.
It is known that with internal fixation of fractures with plate and screw devices it is desirable to apply a compressive force across the fracture site. Bone is a viscoelastic material and support of the structure and transmission of load is the mechanical function of bone. Bone is strongest in compression and weakest in tension. When a compressive force is applied across a fracture site it allows the fractured segments of bone to be placed in close proximity and the compressive force stimulates the bone in healing. If compression is applied at the fracture site, the intimate contact of the bone fragments restores the structural stability of the bone and allows the direct transfer of force from fragment to fragment rather than only through the implant. A compressive force applied directly at the fracture site hastens the healing of bone by encouraging the formation of new osteons which bridge the fracture line promoting a primary type of bone healing.
Some bone fracture realignment procedures involve insertion of a wire into the medullary canal which is then guided through the bone segments often in conjunction with a partially inserted nail for leverage. When the segments are aligned, the nail is fully inserted and the wire is withdrawn.
Metal intramedullary devices, which function as internal splints, have been used for many years to align fractures of tubular bones. These devices may take the form nails, U.S. Pat. No. 5,034,013; tubular members, U.S. Pat. No. 4,467,794; or a multiple pin device, U.S. Pat. No. 4,457,301. A steerable intramedullary fracture reduction device having an elongated shaft with a steerable tip pivotally mounted to the distal end of the shaft is shown by U.S. Pat. No. 5,002,543. In this patent, a tip actuating apparatus near the proximal end of the shaft enables the operator to steer the tip and the shaft into successive segments of the fractured bone, even when the segments are transversely or rotationally displaced so that the segment can be aligned by the shaft. Metal compression devices which are used for fractures are shown by U.S. Pat. Nos. 4,275,717; 4,227,518; 3,779,239 and 3,760,802. The aforenoted metal compression devices are generally directed towards a threaded rod which is inserted within the medullary canal of a fractured tubular bone. The rod is provided with a distal end having an expandable spreadable sheath or fingers which expand upon rotation of the rod. The proximal end of the rod is located outside of the bone and is provided with a nut which holds the rod in place inside the bone thereby causing the fractured bone portions to be held together. U.S. Pat. No. 4,946,459 shows an intramedullary device for fixing and extending separated portions of a long bone within the body of a patient. The device has a tubular sleeve which is nailed to one end of the bone and an adjustment assembly with a moveable member which bears against an end of the nail. The moveable member can be moved from outside the patient to adjust the separation between the portions of the fractured bone.
The aforementioned prior art devices have metal fingers or sleeves which engage the walls of the medullary canal of the bone with deleterious effects.
The use of such prior art intramedullary devices involves the reaming of the medullary cavity which has the effect of destroying the inner lining of blood vessels. Furthermore the ends of long bones in children are also the growth center of the bones. Drilling or gouging through the ends causes damage and may stop or deform further growth.
Other prior art devices currently use dynamic compression plates and screw devices to apply compression across the fracture site. However, for insertion of this type of device, it is necessary to make a large surgical incision over the outer cortex of the bone directly at the fracture site. Placing this type of fixation device entails the disturbance of the soft tissues overlying the fracture site, disturbance of the fracture hematoma, and stripping the periosteium of bone which compromises the blood supply to the bone at the fracture site.
A flexible bladder device has been described by U.S. Pat. No. 4,313,434 to align fractures intramedullarly. However, this bladder device is designed to be placed directly at the fracture site to provide fixation. The bladder device was not designed for compression at the fracture site and when inflated at the fracture site actually promotes separation of the fracture fragments and has the opposite effect of the present balloon catheter compression device.
There is no known intramedullary device currently available that applies a compressive force at the fracture site in addition to aligning the fracture.